This invention relates to sight glasses, and in particular, to sight glasses for use with pressurized vessels, such as boilers.
Sight glasses are often used in conjunction with pressure vessels to observe the liquid level in the vessel. A few designs provide an entry port for probes and sensors used to control vessel temperature, pressure, etc. Commercially available sight glasses presently have a single chamber in communication with the interior of the vessel. This exposes the glass of the sight glass and the probes to wet steam from the vessel. In operational use, the hot, wet steam often either condenses on the glass, or etches the glass permanently, making it difficult to observe the liquid and probes contained within the sight glass. The steam also will cause the liquid in the sight glass to bubble or boil resulting in false readings, both from the probe and visual observation, as to the true liquid level in the vessel. The direct contact of the wet steam on the probes may also result in other false readings. The false readings make control of the process in which the vessel is incorporated difficult.